钙钛矿型稀土复合氧化物催化活性研究进展

概述了近年来对钙钛矿型稀土复合氧化物催化活性研究的进展。研究发现,与其他催化剂相比,钙钛矿型稀土复合氧化物作为燃烧催化剂时,特别是对大气污染物降解具有较好的催化活性,而钙钛矿型稀土复合氧化物作为光催化剂时,对水体污染物降解方面具有很好的光催化作用,具有很大的应用价值。     

稀土钙钛矿型复合氧化物催化剂研究现状(Ⅱ)

综述了近年来国内外稀土钙钛矿型复合氧化物的研究进展，研究了ABO，稀土钙钛矿型催化剂对各种气体的催化效果及反应机理，并讨论了催化剂的S与P的中毒机理。对稀土钙钛矿型催化剂的优缺点以及当前需要解决的问题进行了分析。     

稀土钙钛矿型复合氧化物催化剂研究现状(Ⅰ)

综述了近年来国内外稀土钙钛矿型复合氧化物的研究进展，阐述了由于ABO3稀土钙钛矿型催化剂A、B位的取代，出现了许多钙钛矿型及类似钙钛矿型晶体结构，增加了氧格空位，提高了钙钛矿型催化剂的催化活性。并且详细介绍了催化剂及其载体的制备方法及工艺。     

天然气催化燃烧催化剂的研究(Ⅱ)

介绍了天然气催化燃烧钙钛矿型氧化物催化剂、六铝酸盐型催化剂以及负载型非贵金属催化剂的研究现状。对于钙钛矿型氧化物催化剂,利用A位取代或调整B位元素的种类及配比、新的技术和方法制备高比表面积或具有纳米结构的钙钛矿型氧化物,是提高其甲烷催化燃烧活性的重要手段。六铝酸盐型催化剂具有很高的热稳定性和甲烷燃烧活性,但起燃温度较高,通过采用将金属Pd负载到六铝酸盐上或改变制备方法,提高其比表面积,以提高其低温反应活性。负载型非贵金属催化剂研究最多的是过渡族金属,其氧化活性、抗毒性能和耐久性都存在问题,需进一步研究。     

负载型LaFeAl11O19-δ催化剂的甲烷催化燃烧性能研究

以共沉淀法制备了磁铅石型六铝酸盐催化剂LaFeAl11O19-δ,以浸渍法、沉淀-浸渍法制备了锰负载的稀土磁铅石型六铝酸盐LaFeAl11O19-δ催化剂.并运用XRD、H2-TPR及BET对其进行了表征,同时采用甲烷燃烧反应作为探针反应考察了三种样品的催化性能.XRD实验结果表明,三种方法均可制备出主相结构为六铝酸盐的催化剂,此外还伴有稀土钙钛矿相或氧化物晶相.锰的负载对催化剂的活性有明显作用,在所制备的样品中沉淀-浸渍法制备的样品甲烷催化活性最佳,其甲烷燃烧T10为458℃,T50为550℃,T90为644℃,浸渍法制备的样品活性其次,但优于纯六铝酸盐LaFeAl11O19-δ催化剂.在锰负载稀土磁铅石型六铝酸盐LaFeAl11O19-δ催化剂中,Mn与Fe之间有良好的协同作用,这种协同作用提高了催化剂的催化性能.     

制备方法对双钙钛矿型催化剂性能的影响

采用溶胶-凝胶法、水热法、共沉淀法和溶胶-凝胶-水热联用法等方法制备了新型稀土钙钛矿型复合氧化物LaSrFeNiO₆,探究不同制备方法对催化剂催化甲烷燃烧性能的影响。通过BET、XRD、SEM、H₂-TPR、FT-IR和TG-DSC等技术对其进行物理性能表征及其催化甲烷燃烧活性测试。结果表明：在不同的制备方法下均可形成完整的双钙钛矿晶型，且不同制备方法下甲烷燃烧转化率和催化活性不同，其中溶胶-凝胶-水热联用法制备的催化剂下甲烷转化率最高，转化温度最低，起燃温度T_10%为355℃,T_90%为536℃。     

改性镧系钙钛矿催化剂强化挥发性有机物催化氧化的研究进展

钙钛矿因其结构稳定并具有优异的物化性质,近年来在催化剂方面的应用受到了广泛关注。本文综述了采用不同方法对镧系钙钛矿进行改性来增强催化剂的活性、抗毒性、稳定性和选择性的研究进展;分析了镧系钙钛矿的结构、表面参数、活性氧和低温还原性对于挥发性有机物转化效率的影响,重点阐述了通过优选钙钛矿的制备方法、制备负载型钙钛矿和掺杂型钙钛矿等改性方法来提高镧系钙钛矿催化剂的性能,由此展望了未来改性镧系钙钛矿催化剂的研究方向：采用非金属元素掺杂或多种强化方法结合制备高效催化剂、利用催化燃烧协同光催化氧化转化挥发性有机物、进一步通过实验和仿真模拟制备理想钙钛矿催化剂催化氧化多种挥发性有机物混合物以满足工业化需求。     

钙钛矿型催化剂去除VOC的性能研究

挥发性有机化合物（VOCs）是大气的主要污染物之一,催化燃烧法是目前研究的处理VOCs的有效方法之一。本研究基于VOCs的催化燃烧进行,用浸渍法制备了性能优良的负载型稀土钙钛矿催化剂La0.8Sr0.2MnO3,以气相色谱为检测手段,用常压气体流动评价装置研究该催化剂对低浓度（100~1000mg/m3）VOC（甲苯）催化燃烧的去除效果。     

单双钙钛矿型甲烷燃烧催化剂制备方法及应用进展

甲烷催化燃烧是一种效率高、污染低的能源利用和废气处理技术.该反应在高温、高空速下进行,对催化剂的结构和性质有特殊要求.钙钛矿型催化剂由于其独特的物理化学性质,在甲烷催化燃烧反应中得到广泛应用.本文主要对溶胶凝胶法和非晶态合金法制备钙钛矿型催化剂作了探讨.最后,对该领域目前存在的问题和未来的研究方向进行了讨论.     

汽车尾气净化催化剂的净化原理与作用机理分析

文章阐述了汽车尾气净化催化剂的净化原理,并以含稀土钙钛矿(ABO3)型催化剂为例,对其作用机理进行了分析,为研究开发符合我国国情的汽车尾气净化催化剂奠定了理论基础。     

钡离子对镍基钙钛矿分解氨的影响

镍基钙钛矿分解氨制取氢气虽有稳定性好、价格低廉的优点,但也有完全分解温度偏高的缺点。为降低完全分解氨制取氢气的温度,实验采用柠檬酸络合法,通过改变A位掺杂离子与掺杂量对LaNiO₃改性,并改变载体及负载量,制备一系列的催化剂。采用XRD、SEM、TEM表征技术进行表征,考察了Ba 含量对催化剂结构与性能的影响。实验表明在催化剂装填量为1mL、空速为10000h^-1、原料气为纯氨的条件下,氨分解的最佳电子助剂离子为Ba、最优催化剂为w(NiO)=20%的La_0.9Ba_0.1NiO₃/MCM-41,氨气完全分解温度由650℃降为575℃。随着Ba掺杂量的增加,催化剂活性先增加,在x=0.1达到最大值,之后减小,掺杂Ba过多催化剂的结构由钙钛矿变为非钙钛矿,非钙钛矿结构的催化剂活性不如钙钛矿。     

Supported nickel catalysts with a controlled molecular architecture for the catalytic reformation of methane

In this work a lanthanum and nickel catalyst having perovskite structure, grown on a γ-alumina carrier, is being presented. The structure of the catalyst was confirmed by XRD. The behaviour of this material under the conditions of steam reforming has been studied and the influence of the temperature, the space velocity and the steam/carbon ratio on the conversion of methane and the product distribution in the process was determined. In all cases at higher temperatures conversions of more than 90% and high selectivities were achieved. The experiments to determine the stability of the catalyst demonstrated that no deactivation in experimental runs of more than 17 h occurred. Additionally a study of the catalyst after the reaction showed that only lowly structured carbonaceous species were formed on the catalyst surface, which is not expected to inhibit strongly the initial catalytic activity.     

Noble metal-doped perovskites for the oxidation of organic air pollutants

Ag-Pt- and Pd-doped LaMnO₃-based perovskite catalysts were prepared and their activity in the oxidation of toluene, n-heptane and ethanol was investigated. The activity of LaMnO₃-based catalyst was very high in the oxidation of each compound tested. The Ag-doped catalyst was the most active in the oxidation of each compound and it displayed the highest BET specific surface area (SSA) also. The influence of Pt or Pd doping on perovskite activity is negligibly small. Pt-doped catalysts are slightly more active while Pd-doped catalysts are slightly less active than the pure perovskite. Thermogravimetric-differential thermal analysis (TG-DTA) for the catalyst precursor indicates that above 500 °C a perovskite structure began to form. The XRD analysis reveals the presence of the LaMnO_3.15 perovskite phase and, additionally, the presence of some metal oxide phases (e.g. La₂O₂CO₃, Mn₂O₃) and carbon. BET SSA measured after the oxidation tests was found to decrease for each catalyst. There was no relation between the chemical composition of the catalyst and the loss of SSA.     

High-throughput approach to the catalytic combustion of diesel soot

A methodology for the evaluation of diesel soot oxidation catalysts by high-throughput (HT) screening was developed. The optimal experimental conditions (soot amount, catalyst/soot ratio, type of contact, composition and flow rate of gas reactants) ensuring a reliable and reproducible detection of light-off temperatures in a 16 parallel channels reactor were set up. The temperature profile measured in the catalyst/soot bed under TPO conditions when the exothermic combustion of soot takes place was shown to provide an accurate measurement of the ignition. Its reproducibility and relevance were checked. The results obtained with a reference noble metal free catalyst (La_0.8Cr_0.8Li_0.2O₃ perovskite) agree very well with literature data. Qualitative mechanistic features could be derived from these experiments, stressing the likely limiting step of oxygen transfer from catalyst surface to soot particulates to ignite the soot combustion. Ceria material was shown to be more appropriate than perovskite one. From an HT screening of a large diverse library (over 100 mixed oxides catalysts) under optimized conditions, about 10 new formulations were found to perform better than selected noble metal free reference materials.     

Pd-doped LaCoO3 regenerative catalyst for automotive emissions control

The effect of partial substitution of Co by Pd in LaCoO₃ perovskite structure (i.e., LaCo_0.95Pd_0.05O₃) and the reductive diffusion of Pd from the bulk of perovskite to its surface, thus forming Pd nanoparticles, on CO and C₃H₈ oxidation present in air (simulated exhaust gas) are reported. X-ray powder diffraction (XRD) analyses confirm the perovskite structure for the catalysts. Scanning electron microscopy (SEM) and BET surface area measurements show that partial substitution of Co by Pd decreases the crystallite size of the perovskite and therefore increases its surface area. H₂-temperature programmed reduction (TPR) experiments reveal that Pd reduces at 135 °C and facilitates the reduction of Co in the perovskite structure. By partial reduction of the Pd containing catalyst at 180 °C for 30 min, the complete oxidation temperatures of CO and C₃H₈ decrease by about 70 and 50 °C, respectively.The reduction duration of the Pd containing catalyst strongly affects the T₅₀ and T₉₀ temperatures (temperatures at which 50 and 90% conversion occurs, respectively) and has an optimum, where it decreases by increasing the reduction temperature of the catalyst.     

四效催化剂La-K-Co-Mn同时去除CO、C_xH_y、PM和NOx的研究

四效催化剂的活性组分La0.8K0.2Co0.7Mn0.3O3的合成温度对柴油烟气的净化效果有较大影响,通过X射线衍射、电子扫描电镜、程序升温、比表面积检测和在线效率检测发现,750℃合成的四效催化剂净化柴油烟气的效果最好。通过K和Mn同时部分取代La Co O3中La和Co,探讨K和Mn对钙钛矿结构和烟气净化效果的影响。比表面积检测发现,涂覆改性γ-Al2O3后,整体式催化剂比表面积增加,催化性能得到有效改善。     

稀土钙钛矿型复合氧化物在汽车尾气净化中的应用

阐述了汽车尾气净化工艺中替代贵金属催化剂的必要性和可能性,评述了稀土钙钛矿复合氧化物在三效催化剂中的作用,指出这类贱金属催化剂是研制、开发三效汽车排气催化剂的重要方向。     

Recent progress in the practical applications of heteropolyacid and perovskite catalysts: Catalytic technology for the sustainable society

Recent progresses in practical applications of (i) supported heteropolyacid and (ii) Pd/perovskite catalysts are described. (i) Two industrial catalytic processes, ethyl acetate and acetic acid syntheses both from ethylene, utilize silicotungstic acid, alone and together with Pd, respectively, carefully supported on silica, and exhibit high performance from green chemical and economical viewpoints. The layer structure of heteropolyacid on silica and physical properties of silica are among the key factors of the high performance. (ii) Pd/perovskite catalyst is applied for the treatment of automotive emission, where the catalyst life is very much elongated by embedding Pd into the perovskite lattice and hence resulted in much reduced usage of Pd. These are good examples of green catalytic technology that will contribute to the sustainable society.     

Fiber-supported perovskites for catalytic combustion of natural gas

Based on previous work, highly performing combustion catalyst consisting of an iron doped nickel–cobalt-based perovskite supported on commercial fiber blankets has been developed. The catalyst is particularly suitable for use in combustion of lean natural gas mixtures. With 12–15 wt% perovskite loadings the catalyst exhibits activities comparable to those of commercial fiber-supported platinum. At temperatures below 1000 K the catalyst activity seems stable, and resistant to low levels of mercaptan used as an odorant. Unlike platinum (or palladium) the catalyst promotes deep methane oxidation, i.e. no carbon monoxide formation, even in methane-rich mixtures. The combustion is inhibited by carbon dioxide, but water has no measurable influence. A simple kinetic model which takes the inhibition effect of carbon dioxide into account and permits more realistic conversion estimates is proposed: r_CO2=k_CH4P_CH4/(1+k_CO2P_CO2).